Method of treating polyolefins



United States. Patent Ofifice 3,305,297 Patented Feb. 21, 1967 3,305,297 METHOD OF TREATING POLYOLEFINS Russell M. Mantell, Princeton, and William L. Ormand, Kendall Park, N.J., assignors to Aero Chem Research Laboratories, Inc., a corporation of Maryland No Drawing. Filed Jan. 7, 1964, Ser. No. 336,134 8 Claims. (Cl. 817) This invention relates to improved methods of treating articles, such as fabrics, made of polyolefins, such as, for example, polyethylene, polypropylene and polybutylene. More particularly, it relates to an improved method of lpretreating this class of materials so that they become more adsorptive toward at least certain classes of dyes.

The polyolefins have proved to be very difiicult to dye, particularly after they are manufactured into fabrics, films or shaped articles. Because of this difficulty, for some time the materials were colored mostly by dissolving or suspending particles of the coloring substance in the polyolefin itself, prior to its further manufacture into fibers,- films or molded articles. Obviously, this method of imparting color has many disadvantages. The manufacturer or fabricator of finished articles had to accept the colors as he received them and could not modify them to suit his own particular needs. thermore, these materials could not then be subjected to further manufacturing steps which might non-uniformly modify the original color, nor could the color be stripped from the material. With increased use of the polyolefins has come a renewed interest in attempting to dye them after they have been manufactured into fibers, fabrics, films or shaped articles.

One method which has been proposed is to treat the articles, first, in an acid bath containing an alkali metal bichromate and then in an acid bath containing a reducing agent. Another method is -to treat the articles in a bath of highly, concentrated sulfuric acid or oleum.

Still another method is to pretreat the articles with fusible and hydrolyza'b'le halides of phosphorus or silicon. Another previously proposed method is to dye the articles with vat dyes in the presence of a hydrocarbon amine. And still another previously proposed method is to treat the polyolefinic articles with an oleophilic organic compound having a molecular weight between 100 and 800 and which contains a basic nitrogen atom.

One object of the present invention is to provide an improved method of dyeing polyolefins such as polypropylene.

Another object of the present invention is to provide an improved method of pre-treating polyolefins for a dyeing operation so that when they are subsequently subjected to the dyeing operation they adsorb a larger quantity of the dye than they would have taken up without the pre-treatment.

Another object of the invention 'is to provide a method of pre-treating polyolefins, in connection with a later dyeing operation, which is simple to use, does not require expensive or complicated apparatus and which is rapid and inexpensive to carry out.

Another object of the invention is to provide an improved method of dyeing polyolefins which produces dyed material resistant to fading due to light, Washing, drycleaning and bleaching.

A principal feature of the present invention is a method which comprises treating polyolefin fabrics or other articles with nitrogen oxides or oxyhalides wherein the ratio of oxygen atoms to nitrogen atoms is at least one, under essentially anhydrous conditions, for brief periods of time, and then subjecting the articles to a conventional dyeing operation, utilizing, preferably, so-called basic dyes. In some cases it is convenient to apply the nitrogen compound in gas or vapor form. In other cases it is preferable to apply it in non-aqueous solution.

The dyes which have been found to be particularly useful in the process of the present invention are socalled basic dyes which are also cationic in nature. Basic dyes have been defined by Venkataraman, The Chemistry of Synthetic Dyes, Academic Press, New York, N.Y., 1952, vol. 1, page 270, as dyes which dye wool from a neutral or weakly acid bath, and also dye cotton mordanted with tannic acid and tartar emetic or with certain synthetic organic mordants. These dyes include ammonium, sulfonium or oxonium salts and their usual acid components are hydrochloric, sulfuric and oxalic acids. The basic nitrogen is in the form of primary or tertiary amino groups or a 'heterocyclic system. Basic dyes of different chemical classes may be obtained by the introduction of amino or dialkylamino groups and conversion into an ammonium salt.

Examples of basic dyes found suitable include: Chrysoidine Y (Color Index No. 11270), Bismark Brown (Color Index No. 21000), Aurom-ine 0 (Color Index No. 41000), Rhoclamine CG (Color Index No. 45160), Safranine Y (Color Index No. 50240), Basic Fuchsin (Color Index No. 42500), Brilliant Cresyl Blue (Color Index No. 51010), Astra Phosphine 56 (Color Index No. 46035), Capri Blue having the chemical formula Malachite Green( Color Index No. 42000), Methyl Green (Color Index No. 42590), Methyl Violet (Color Index No. 42532), Methylene Blue (Color Index No. 52015), Methylene Green (Color Index No. 52020), Neutral Red (Color Index No. 50040) and Victoria Blue R (Color Index No. 44040).

To test the method of the present invention, spun polypropylene cloth was cut into 3 x 3 inch squares which were then exposed to treating substances within the scope of the present invention. In the case of normally gaseous materials, the treatment was conducted at ordinary room temperature.

In all cases the cloth sample was allowed to remain in contact with the treating substance for about 30 seconds. The excess material adsorbed on the cloth surface was subsequently allowed to evaporate. After being treated as described, in accordance with a feature of the invention, each sample was then dyed with one of the basic cationic dyes.

The dyeing process consisted of immersing the treated samples in a 1% by weight aqueous solution of the dye, which was held at l00 C., with stirring, for 20 minutes. The dyed samples were then rinsed and soaped in tap water until essentially no color was observed in the wash water. They were then immersed in a 2% deter-gent solution, brought to a boil, immediately rinsed in tap water, and brought to a boil again in a fresh 2% solution of detergent. After a second rinse in tap water, the samples were dried and were ready for testing for fastness.

In the case of all of the dyes listed above as specific examples, pre-treatment of polypropylene cloth, in accordance with the method of the invention, resulted in noticeably more adsorption of dye than was obtained by untreated cloth. The dye adsorption was not improved to the same extent for all of the dyes, but all of the dyed samples showed a significant increase in dye adsorption. Also, the various pre-treating substances exhibited diflerent degrees of effectiveness compared to each other and with different dyes.

A specific example of treatment in accordance with the present invention is as follows.

Example A 3 x 3 inch square of essentially pure isotactic, unmodified polypropylene cloth was immersed in a 1000 cc. Erlenmyer flask filled with nitrogen dioxide gas at 25 C. and atmospheric pressure. After 30 seconds the cloth was removed from the flask, waved in the air to remove excess nitrogen dioxide, and immediately immersed in a 1% by weight solution of Malachite Green at 80-100 C. and stirred. After 20 minutes the cloth was removed and alternately rinsed in running tap water and soaped with 2% by weight aqueous Tide solution until color was no longer visibly removed. The dyed cloth was then brought to a boil in 2% by weight aqueous Tide solution and immediately rinsed in tap water. This latter procedure was repeated. Excess water was then removed from the cloth by squeezing between absorbent paper towels and the cloth was then permitted to dry.

The above procedure was also used with Neutral Red, Methyl Violet, Brilliant Cresyl Blue, Capri Blue, and Basic Fuchsin. Each of these dyes produced a fast, deep and brilliantly colored cloth.

The cloth samples, dyed as described above, were subjected to standard washing, bleaching and drycleaning tests in order to test color fastness.

Wash test Test used: AATCC Standard Test Method 36-1961. Test III, page B-80, AATCC Technical Manual, 1963. The test consists essentially of washing in 0.5% by weight neutral soap and 0.2% by weight sodium carbonate solution at 160 F. for 45 minutes, rinsed several times in water and once in 0.014% acetic acid solution, wringing out and pressing dry.

All of the dyed samples showed good dye retention after being subjected to this test.

Bleach test Test used: AATCC Standard Test Method 3-4962, Test III, page 3-57, AATCC Technical Manual, 1963. The test consists of washing in 0.3% available chlorine solution at 80 F. for one hour, rinsing thoroughly and allowing to stand for minutes in 1% by weight sodium bisulfite solution at 80 F., rinsing, wringing out and pressing dry.

The dyed samples showed excellent color retention after being subjected to this test.

Drycleaning test Test used: AATCC Standard Test Method 85-1963, page B-61, 1963, AATCC Technical Manual. The test consists of washing in perchloroethylene at 115 F. for 30 minutes, blotting excess liquid from the sample, air drying and then pressing.

The dyed samples again showed excellent color retention after undergoing this test.

Light-fading test The resistance of the dyed samples to light-fading was also tested by exposing to a (General Electric Company) RS reflector sunlamp held 24 inches from, and perpendicular to, the sample surface. One-half of each sample was covered so that the light could not strike it and the covered half was used for comparison purposes. Although the dyes differed greatly in their response to this test, all showed good resistance to fading.

Other nitrogen compounds which are suitable for use in the method of the present invention are nitric oxide (NO), nitrogen trioxide (N 0 and any of the corresponding halogen derivatives of these oxides such as nitrosyl chloride (NOCl).

What is claimed is:

1. A method of dyeing an article made of a polyolefin comprising pre-treating said article with a substance selected from the class consisting of nitrogen oxides and nitrogen oxyhalides wherein the ratio of oxygen atoms to nitrogen atoms is at least one, and then dyeing said article in an aqueous solution of a basic dye.

2. A method of dyeing polyolefin cloth comprising pretreating said cloth with a substance selected from the class consisting of nitrogen oxides and nitrogen oxyhalides wherein the ratio of oxygen atoms to nitrogen atoms is at least one, and then dyeing said cloth in an aqueous solution of a basic, cationic dye.

3. A method of dyeing an article made of isotactic polyolefin comprising pre-treating said article with nitrogen dioxide under essentially anhydrous conditions and then dyeing said article in an aqueous solution of a basic, cationic dye.

4. A method of dyeing polyolefin cloth comprising pretreating said cloth with nitrogen dioxide, under essentially anhydrous conditions, for a brief period of time, and then dyeing said article in an aqueous solution of a basic, cationic dye.

5. A method of dyeing an article made of polypropylene comprsing pre-treating said article with a substance selected from the class consisting of nitrogen oxides and nitrogen oxyhalides wherein the ratio of oxygen atoms to nitrogen atoms is at least one, and then dyeing said article in an aqueous solution of a basic dye.

6. A method of dyeing polypropylene cloth comprising pre-treating said cloth with a substance selected from the class consisting of nitrogen oxides and nitrogen oxyhalides wherein the ratio of oxygen atoms to nitrogen atoms is at least one, and then dyeing said cloth in an aqueous solution of a basic, cationic dye.

7. A method of dyeing an article made of isotactic polypropylene comprising pre-treating said article with nitrogen dioxide under essentially anhydrous conditions, and then dyeing said article in an aqueous solution of a basic, cationic dye.

8. A method of dyeing propylene cloth comprising pretreating said cloth with nitrogen dioxide, under essentially anhydrous conditions, for a brief period of time, and then dyeing said cloth in an aqueous solution of a basic, cationic dye.

References Cited by the Examiner UNITED STATES PATENTS 1/ 1966 Karn. 1/1966 Cappuccio et al. 8-55 

1. A METHOD OF DYEING AN ARTICLE MADE OF A POLYOLEFIN COMPRISING PRE-TREATING SAID ARTICLE WITH SUBSTANCE SELECTED FROM THE CLASS CONSISTING OF NITROGEN OXIDES AND NITROGEN OXHYALIDES WHEREIN THE RATIO OF OXYGEN ATOMS TO NITROGEN ATOMS IS AT LEAST ONE, AND THEN DYEING SAID ARTICLE IN AN AQUEOUS SOLUTION OF A BASIC DYE. 